Chamber matching is a condition where the output of multiple plasma processing chambers, in terms of properties of devices produced, are exactly matched within the specification.
In a manufacturing environment, a process recipe is typically tuned to match metrology values such as critical dimension (CD) and etch rate (ER). This approach, however, requires at least taking processed substrates from the process line, for testing and metrology, resulting in lost productivity. Furthermore, some metrology techniques are destructive, by nature, resulting in lost revenue due to substrates being destroyed to verify etch rate (ER), and even more importantly, critical dimension (CD). The need exists for a diagnostic that would allow chamber matching and process tuning to be ascertained without the time-consuming routing of processed substrates to metrology stations, or the even more costly destructive metrology techniques. Such novel diagnostics would leverage data collected from existing sensors on the plasma processing chamber, to ensure chamber matching and in-spec critical dimension (CD) and etch rate (ER).
In prior art chamber matching, matching module-level sensor values, such as, for example, matching capacitance positions on the match network, do not guarantee matching of the plasma parameters during device production, and hence produced device characteristics. Sensor to sensor variations typically make direct matching of sensor values not useful. Furthermore, the use of statistical fault detection systems requires a user-defined boundary to be defined between normal and abnormal states, for example between normal and abnormal plasma states, as defined by CD metrology data obtained from processed devices. Since there do not exist direct links between, the parameters (controlled and measured), and critical dimension (CD), there is a tendency for such systems to over-diagnose faults. In other words, an increase of the frequency of fault detections may occur when, in-fact, the produced devices are still within-specification. For example, some benign parameter excursion can trigger a false fault detection. Or, in terms of application in chamber matching, post-maintenance seasoning, etc., a slight mismatch of some parameter which is not detrimental to produced device characteristics may cause maintenance personnel to not return the chamber into production for an extended period of time, resulting in unnecessary revenue loss. To address the above shortcomings, the invention described herein establishes a more reliable boundary between normal conditions, and faulty or mismatched chamber state, based on a more direct linkage between plasma parameters and critical dimension (CD).
Accordingly, what is needed, as recognized by the present inventor, is a method and a system capable of minimizing device performance mismatch by matching plasma conditions across multiple chambers.
The foregoing “Background” description is for the purpose of generally presenting the context of the disclosure. Work of the inventor, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.